Currently, the mechanisms for adjusting the optical paths of the optical sensors were mostly developed toward multi-directional adjustment. For example, the technical field associated with adjustment of the optical path of a CCD optical module comprises at least two major types of technologies.
A first mechanism for adjusting the optical path of a CCD optical module is described in Taiwanese Patent Publication No. 407826, entitled “Adjustable fixing device of a CCD plate”. Such an optical path adjustable mechanism can adjust the CCD plate in five degrees of freedom, including movement in the z-axial direction (upward or downward movement), movement in the y-axial direction (leftward or rightward movement), rotation on the yz-plane (vertical rotation), rotation on the xy-plane (horizontal rotation) and movement in the x-axial direction (forward or backward movement). In this way, the external light beam is substantially perpendicular to the CCD optical sensor, thereby obtaining the desired relative distance or angle and achieving good imaging performance. This optical path adjustable mechanism described above still has some drawbacks. For example, since a complicated five-axial adjustable jig is necessary for mass production and the components thereof are plentiful, this mechanism is not suitable to use in the industry. In addition, prior to the complete adjustment, it takes a period for hardening an adhesive agent so as to fix the optical path adjustable mechanism. In other words, this optical path adjustable mechanism is not cost-effective.
In order to save cost and reduce the productive complexity, another optical path adjustable mechanism was developed. A second mechanism for adjusting the optical path of a CCD optical module is described in Taiwanese Patent No. 500279, entitled “Four-direction adjustable optical module”. The optical module comprises a carriage and a CCD module. In contrast to the optical module described in Taiwanese Patent No. 407826, the carriage comprises a coupling window for connecting with the CCD module. A screw hole and a resilient element (e.g. a spring) are provided on each of bilateral sides of the coupling window. The spring protrudes from the surface of the coupling window. When the CCD module and the coupling window are assembled, a screw penetrates through the CCD module and is then screwed into the screw hole. At that time, the resilient element within or beside the screw hole will deform according to the stress from the screw. Because these two screws are separately screwed, the CCD module can be adjusted to rotate horizontally on the xy-plane. The optical module can be adjusted to move in four directions including upward or downward movement, leftward or rightward movement, vertical rotation and horizontal rotation. By adjusting the optical focus of the CCD module, the forward or backward movement is feasible.
Since the screw penetrating through the screw hole has a uniform thread pitch, the resolution to be adjusted will be limited by the uniform thread pitch. Take a M3 pitch screw for example. Since the pitch of this screw is 0.5 mm, the CCD module will advance or return in an amount of 0.5 mm for each revolution of the screw. As known, with increasing development of the CCD optical sensor, the pixel distance becomes shorter and shorter to meet the requirement of achieving higher resolution. Since this amount of pitch adjustment is too large, the short pixel distance is not obtainable. On the other hand, another type of screw having a smaller thread pitch may be utilized to obtain a more precise resolution adjustment. This specified type of screw, however, is not readily available and the cost thereof is increased.